text: As shown in the diagram, a number of baffles are used throughout to remove possible stray light being reflected off the sides of the beamline tube.  The use of only one mirror minimizes the loss of photon flux which is most important in the VUV region where reflectivity is poor relative to the visible wavelength range.
  The first constructed SRCD beamlines initially tried to utilize the intrinsic properties of the SR radiation produced, whereby there exists a "central" linearly-polarized component with, above and below this, equally opposing regions of circularly-polarized components.  The premise for this was that the overall signal produced from a chiral sample would be enhanced by the absorption difference (the signal) derived from these circularly polarized features of the beam.  In an ideal situation this approach would work; however, this setup was modified such that all beamlines now include a linear polarizer (as shown) to remove these circularly polarized components.  This was because even the minutest of movements in beam position (beam drift) led to unequal matching of the contributions of the circularly polarized components striking the sample and this, in turn, meant the SRCD signal produced was inaccurate and unreliable; often being irreproducible as a result.
  Whereas cCD machines are purged throughout with nitrogen to minimize the absorption by oxygen of the light from the source xenon arc lamp, in an SRCD arrangement the beam passes through a calcium fluoride (CaF), or similar "VUV-wavelengths transparent", window where everything before this point is in vacuum, and everything beyond is in nitrogen. The beam interacts with a photoelastic modulator (PEM) which consequently produces an alternating right- then left-circularly polarized beam and these now interact with the sample.  The resultant absorption difference by the sample is measured and amplified by a photomultiplier tube (PMT) and from this the SRCD spectrum is recorded.
  The wavelength range that is utilized for SRCD studies is typically in the UV to VUV region and can go to below this; potentially from ~100 nm, up to the visible region, ~400 nm.  The exact range over which data can be collected relies on the beamline set up, the sample preparation and the wavelength range of the PMT detector used.  One of the primary factors limiting the lower wavelength cut off is the sample usually being in solution as a large water absorption band exists centred ~167 nm.  This high absorption background swamps any possibility of measuring the very small CD difference signal, although use of deuterated water (DO) as the solvent reduces the solvent absorption increasing the lower wavelength data collection range by ~10 nm.  Removing the solvating water completely, creating a film as a result, means that data can be recorded to significantly lower wavelengths, down to around ~130 nm.